A company uses $3$ trucks to deliver a total of $T$ liters of cement. Each truck can transport $x$ liters of cement per trip, and makes a total of $y$ trips. Write an equation that relates $T$, $x$, and $y$.
Explanation: Let's look at the volume of cement transported with a single truck. A single truck transports $x$ liters of cement every trip, and it does $y$ trips. So in total, it transports $xy$ liters: $\begin{aligned} &\phantom{=}\left(x\,\dfrac{\text{liters}}{\text{trip}}\right)\left(y\,\text{trips}\right) \\\\ &=xy\,\dfrac{\text{liters}}{\cancel\text{trip}}\cdot\,\cancel\text{trips} \\\\ &=xy\,\text{liters} \end{aligned}$ Since there are $3$ trucks, the total volume of transported cement is $3xy$ : $T=3xy$